Looks like you should be able to enter without testing if you're fully vaccinated https://en.coronasmitte.dk/travel-rules/covidtravelrules Or if not self-isolate for 10 days or 6 if your PCR comes back. Kids under 15 years of age are exempt. I think the rules are relaxing more in a few week, so depends a bit when you're traveling as well. If you just want to self test then all supermarkets carry antigen test for about 3 pound each.